Carburetor assembly



June 17, 1958 M. F. STERNER 2,339,154

CARBURETOR ASSEMBLY Filed Nov. 28, 1955 INVENTOR.

MELVIN F. STERNER BY mag, wvgfly A TTORNEYS United rates Patent 9 HolleyCarburetor Company, Detroit, Mich, a corporation of Michigan ApplicationNovember 28, 1955, Serial No. 549,334

7 Claims. (Cl. 18320) The present invention relates to a carburetorassembly, and more particularly to a carburetor assembly adapted toavoid difficulties previously encountered as a result of percolationresulting from hot soaking.

More specifically, it is an object of the present invention to providein a carburetor having an air cleaner, an air passage extending from thefloat bowl to a point within the air cleaner adjacent the inlet to thecarburetor barrel, and a check valve controlled vent in the air passagecommunicating with atmosphere.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawings, wherein:

The figure is a diagrammatic sectional view of a portion of acarburetor.

Referring now to the drawings the invention is illustrated inconjunction with a carburetor of conventional type herein illustrated ascomprising a barrel 10 provided with a venturi the throat of which isindicated at 12. Flow of air through the barrel is controlled by athrottle 14 and a main nozzle 16 is provided adjacent the throat of theventuri.

The carburetor construction comprises a bowl or float chamber 20 havinga float 22 therein controlling an inlet valve (not shown) adapted tomaintain the level of fuel substantially as illustrated in the drawing.

Adjacent the bottom of the bowl 20 is a main jet 24 providing arestricted inlet into the main well 26. At its upper end the main wellcommunicates with a main fuel supply passage 28 extending to the nozzle16. An idle jet 30 communicates with an idle well 32 which in turncommunicates with the idle fuel supply passage 34 extending to idle andtransfer ports 36 and 38 respectively. Main and idle air bleeds areindicated at 40 and 42 respectively, the main air bleed communicatingwith the main well by a transverse passage indicated at 44.

Associated with the carburetor is an air cleaner 50 of usual type whichis filled with air filtering material adapted to filter dust and otherparticles out of air as it is drawn into the inlet end of the barrel 10.As a result of substantial air flow through the air cleaner, it will beappreciated that there is a substantial drop in pressure of air as itpasses through the air cleaner. In other words, the pressure of air atthe inlet to the bowl or venturi of the carburetor is appreciably belowatmospheric pressure. Morever, this pressure differs from atmosphericpressure by an amount which is a function of air flow through thecarburetor.

The actual supply of fuel to the venturi occurs as a result of partialvacuum or sub-atmospheric pressure existing at the throat of the venturiand the pressure of air on the upper surface of the fuel in the floatchamber.

Where atmospheric pressure was admitted directly to the bowl, thepressure diflerential effective on the main nozzle was not dependentsolely on air velocity, since a "ice variable and substantial pressuredrop occurred across the air cleaner.

In accordance with the present invention the bowl 20 is provided with anair passage 52 extending from the upper part of the float bowl to a port53 within the air cleaner in proximity to the air inlet from the aircleaner to the upper end of the barrel 10. As a result of thisconstruction the air pressure acting on the fuel contained in the bowlis the same or substantially the same as the pressure of air existing atthe inlet to the barrel of the carburetor. Thus, any pressure dropoccurring across the air cleaner is ineffective to produce variations inthe pressure differential which acts to force fuel through the nozzle16.

However, the construction as thus far described is not satisfactory as aresult of its functioning during hot soaking. If the engine has beenrunning a substantial time and has reached relatively high temperatureand is then shut ofi, the transfer of heat by conduction or otherwise toall parts of the engine including the carburetor, results in vaporizingor in some cases actual percolation of the liquid fuel contained in thebowl. With the construction as thus far described, the liquid fuel orits heavy vapors would be forced through the air passage 52 into the aircleaner. Since the upper end of the air passage 52 is adjacent the upperor inlet end of the carburetor barrel, these vapors would in generalflow down through the venturi and unless the throttle 14 were completelyclosed, they would flow into the manifold. The result of this is thatwhen an attempt is made to start the engine, the initial supply of fuelto the cylinders would be too rich and the engine would fail to fireuntil continued cranking exhausted the over-rich mixture.

In accordance with the present invention, a vent passage 54 is providedextending from an intermediate portion of the air passage to atmosphere.The vent passage 54 has at its lower end a port 56 opening toatmosphere. It will be observed from the figure that the port 56 isdirectly above the upper wall 58 of the bowl. This upper wall isprovided with an upwardly open downwardly extending well or recess 60which receives the guide stem 62 of a very light gravity biased checkvalve 64. When the engine to which the carburetor is attached is notrunning, the check valve 64 will occupy the illustrated position atwhich time the vent passage 54 is open to atmosphere. Accordingly, asgasoline vapors boil off from the bowl 20 to pass out the vent passage54 to atmosphere, passage of the vapors into the interior of the aircleaner is at a minimum since the nature of air cleaners offersresistance to flow of the vapors, and such flow through the vent passage54 to atmosphere is totally unrestricted. Moreover, it will be observedthat the vent passage 54 is inclined downwardly and the troublesomevapors which lead to difiiculties in restarting the engine are ingeneral heavier than air so that they tend to flow by gravity throughthe downwardly inclined vent passage 54.

When however, the engine to which the carburetor is attached is startedthere is an immediate substantial flow of air through the carburetorbarrel, drawing air from atmosphere through the air cleaner. As a resultof resistance to flow through the air cleaner, the air pressure existingat the upper end of the air passage 52 is appreciably below atmospheric.This air pressure is communicated to the interior of the bowl andsupplies the major pressure efiective to cause fuel to flow out of thenozzle against the reduced pressure of vacuum existing at the throat ofthe venturi. A second effect of the reduced pressure existing at theport 53 of the air passage 52 is a pressure difference between the port53 and the port 56 in the vent passage 54. As a result of this, airunder atmospheric pressure tends to enter the vent passage 54 3 and toflow upwardly therethrough into the interior .of the air cleaner.However, the check valve 64 is designed to move to closed position upona minimum flow of air so'that during operation of the engine, the checkvalve is retained by atmospheric pressure in its upper or closedposition against the port 56.

The drawings and the foregoing specification constitute a description ofthe improved carburetor assembly in such full, clear, concise and exactterms as to enable any person skilled in the art to practice theinvention, the scope of which is indicated by the appended claims.

What I claim as my invention is: t

l. A carburetor for an internal combustion engine having a barrelincluding a venturi, a fuel bowl, a nozzle in the venturi of saidbarrel, a passage connecting said bowl and nozzle, an aircleanerdisposed at the inletend of said barrel, an always open air passageextending upwardly from the upper part of said bowl to a position withinsaid air cleaner adjacent the inlet end of said barrel to subject thefuel in said bowl to an air pressure equal to atmospheric pressure lessthe pressure drop through said air cleaner, a vent passage connectingsaid air passage at a point below the top thereof to atmosphere, and acheck valve in said vent passage disposed to prevent entrance of airinto said air cleaner through said vent whenever the engine is runningand irrespective of throttle position. a p i Y 2. A carburetor asdefined in claim 1 in-which said check valve is gravity biased towardopen position.

3. A carburetor as defined in claim 1 in which the vent passage extendsdownwardly from its port connecting to the air passage to its port toatmosphere.

4. A carburetor for an internal combustion engine having a barrelincluding a venturi, a fuel bowl, a nozzle in the venturi of saidbarrel, a passage connecting said bowl and nozzle, an air cleanerdisposed at the inlet end of said barrel, an air passage extendingupwardly from the upper part of said bowl to a position within said aircleaner adjacent the inlet end of said barrel and to a point appreciablyabove the bottom of the air cleaner to subject the fuel in said bowl toan air pressure equal to atmospheric pressure less a pressure dropsubstantially equal to that through said air cleaner, a'vent'passageconnecting said air passage at a point below the top thereof toatmosphere, said vent passage extending downwardly from its point ofconnection to the air passage to its port to atmosphere, the port ofsaidvent passage connecting to atmosphere being located 'at the bottomof said air cleaner, and a check valve in said vent passage disposed toprevent entrance of air into said air cleaner through said vent when theengine isrunning.

5. A carburetor for an internal combustion engine having a barrelincluding a venturi, a fuel bowl, 'a nozzle in the venturi of saidbarrel, a passage connecting said bowl and nozzle, an air cleanerdisposed at the inlet end of said barrel, an air passage extending fromthe upper part of said bowl to a position within said air cleaneradjacent the inlet end of said barrel to subject the fuel in said bowlto an air pressure equal to atmospheric pressure less the pressure dropthrough said air cleaner, avent passage connecting said air passage toatmosphere, and a check valve in said vent passage disposed to prevententrance of air into saidair cleaner, through said vent when the engineis running, said air cleaner being located directly over said bowl, theupper wall of said bowl having an upwardly open valve retaining recesstherein, said vent passage having aport directly above said recess, saidcheck valve having a guide portion in said recess and a valve portionmovable upwardly by atmospheric pressure when pressure Within saidtaircleaner is reduced by flow of air therethrough;

6. A carburetor for an internal combustion engine having a barrelincluding a venturi, a fuel bowl, a nozzle I e in the venturi of saidbarrel, a passage connecting said I e in the venturi of said barrel, apassage connecting said ing upwardly at the side of said carburetorbarrel to a I point substantially above the inlet end of said carburetorbut substantially removed from the area of air admission into said aircleaner, and said vent passage extending from adjacent theupper end ofsaid air passage: roan atmosphere port located at the bottom ofsaid aircleaner. 7. A carburetor for an internal combustion engine having abarrel including a venturi, a fuel bowl, a nozzle bowl and nozzle, anair cleaner disposed at the inlet end of said barrel, an air passageextending from the upper part of said bowl to a position within said aircleaner adjacent the inlet end of said barrel to subject the fuel insaid bowl to an air pressure equal to atmospheric pressure less thepressure drop through said air cleaner, a vent passage connecting saidair passage to atmosphere, and a check valve in said vent passagedisposed to prevent entrance of air into said air cleaner throughsaidvent when the engine is running, the atmosphere port of said ventpassage being located directly above the top wall of said bowl, and saidcheck valve being'partly disposed in a locating recess provided in saidtop wall.

' References Cited in the file of this patent UNITED STATES PATENTS2,316,882 Moseley et al. Apr. 20, 1943 Miller 'Ju1y 13, 1954

